This invention relates generally to superconductive magnets and more particularly, to thermal shield suspensions for use in superconductive magnets.
Superconductive magnets include superconductive coils which generate uniform and high strength magnetic fields, such as are employed in magnetic resonance imaging (MRI) systems for medical diagnostics. Within at least some known magnets, the superconductive coil assemblies are enclosed in a thermal shield surrounded by a vacuum enclosure. Various designs of tube suspension systems are employed to support the superconductive coil assembly such that the magnet is maintained a pre-determined distance from both the thermal shield and the vacuum enclosure.
The suspension systems include a plurality of straps and bolts rigidly connected together to support the superconductive coil assembly and the associated components, i.e. the thermal shield and vacuum enclosure. The suspension systems are subjected to stresses from supporting the weight of the components and during operation, such systems may also be subjected to thermal stresses induced between components. Additionally, vibrational stresses may also be induced into the suspension system during operation. Overtime, continued operation with such stresses may cause premature failure.
To facilitate preventing such failures, at least some known suspension systems include extensive damping systems to minimize the effects of the stresses. However such damping systems are expensive and increase the overall cost of manufacture.
In one aspect a method for assembling a thermal shield suspension assembly including a plurality of straps, wherein the straps are arranged in an alternately cross hatch arrangement such that a plurality of first straps extend at a first orientation with regards to the cryogenic vessel and a plurality of second straps extend at a second orientation with regards to the cryogenic vessel, and wherein the first orientation is different from the second orientation and each second strap is disposed between the adjacent first strap is provided, the method comprising securing the first strap including the tensioning block to a thermal shield flange and a cryogenic vessel flange and securing the second strap to the thermal shield flange and the cryogenic vessel flange.
In another aspect a superconductive magnet is provided that includes a superconductive coil assembly including a cryogenic vessel, wherein the cryogenic vessel includes at least a flange, a thermal shield enclosing the coil assembly, wherein the thermal shield includes at least one flange, a vacuum enclosure enclosing the thermal shield, and a thermal shield suspension assembly positioned between the cryogenic vessel and the thermal shield. The thermal shield suspension assembly includes a plurality of straps configured to facilitate damping vibrational forces induced to the magnet. The straps are arranged in an alternately cross hatch arrangement such that a plurality of first straps extend at a first orientation with regards to the cryogenic vessel and a plurality of second straps extend at a second orientation with regards to the cryogenic vessel, wherein the first orientation is different from the second orientation and each second strap is disposed between the adjacent first strap.
In a further aspect a thermal shield suspension assembly for a superconductive magnet is provided, the assembly includes a superconductive coil assembly including a cryogenic vessel, wherein the cryogenic vessel includes at least a flange, a thermal shield enclosing the coil assembly, wherein the thermal shield includes at least one flange, and a plurality of straps. The straps are positioned between the cryogenic vessel and the thermal shield and configured to dampen vibrational and hyper-sonic sound responses induced in the magnet, the straps are arranged in an alternately cross hatch arrangement such that a plurality of first straps extend at a first orientation with regards to the cryogenic vessel and a plurality of second straps extend at a second orientation with regards to the cryogenic vessel, wherein the first orientation is different from the second orientation and each second strap is disposed between the adjacent first strap.
In yet another aspect, a plurality of thermal shield suspension straps are provided, wherein the straps are arranged in an alternately cross hatch arrangement. A first strap includes a first end, a second end, and a unitary elongate body extending therebetween, the first end includes a tensioning block, and the first strap extends at a first orientation with regards to a cryogenic vessel. A second strap includes a first end, a second end, and a unitary elongate body extending therebetween, and the second strap extends at a second orientation with regards to the cryogenic vessel, wherein the first orientation is different from the second orientation and each second strap is disposed between the adjacent first strap.